Kinetics of the gas‐phase reaction CH3F + I2 ⇆ CH2FI + HI: The CH bond dissociation energy in methyl and methylene fluorides

Pickard, James M.; Rodgers, A. S.

doi:10.1002/kin.550150607

Cited by 38 publications

(8 citation statements)

References 25 publications

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“…The derived C-H bond dissociation energies show the well-accepted trend of decreasing bond strength with bromine substitution, a trend that is also observed with chlorine substitution but just the opposite of which is seen with fluorine substitution. 55,56,62,63 There is some difference in our derived C-Br bond dissociation energies for CH 2 Br 2 and CHBr 3 from values reported in the literature, with our values being lower by approximately 2 and 3 kcal/mol, respectively. The derived DH°(CH 2 Br-Br) ) 69.8 ( 2 kcal/mol by Tschuikow-Roux and Paddison 55 is too high because, as pointed out earlier, they adopted the estimated ∆H°f ,298 (CH 2 Br 2 ,g) of Bickerton et al 53 Furuyama et al 58 have already pointed out that the DH°-(CHBr 2 -Br) ) 66 ( 4 kcal/mol reported by Miller and Palmer 61 is too high, and in fact in their analysis adopted the minimum value of 62 kcal/mol.…”

Section: H°-h°0 (Kcal Molcontrasting

confidence: 70%

Structures, Vibrational Frequencies, Thermodynamic Properties, and Bond Dissociation Energies of the Bromomethanes and Bromomethyl Radicals: an Ab Initio Study

Paddison

Tschuikow‐Roux

1998

J. Phys. Chem. A

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Reported here is a theoretical study of the entire series of bromomethanes (CH4 - n Br n ) and bromomethyl radicals (CH3 - m Br m ) establishing a self-consistent set of structural and thermodynamic information. Ab initio molecular orbital calculations were performed to compute equilibrium geometries for the molecules and radicals initially at the (U)HF/6-31G* and (R)HF/6-31G* levels, respectively, and then refined at the MP2/6-31G* level. Vibrational frequencies were determined for all species at the HF/6-31G* level and comparison with infrared measurements and matrix isolation studies is favorable. Electron correlation contributions were performed by single-point calculations using fourth-order Møller−Plesset perturbation theory for derived MP2/6-31G* geometries. Enthalpies of formation were obtained from a consideration of applicable isodesmic reactions using the derived MP4/6-31G**//MP2/6-31G* total energies in conjunction with experimentally established enthalpies of formation for CH3Br, CH4, and CH3 •. The calculations predict the following standard enthalpies of formation in kilocalories per mole (at 298 K and 1 atm): CH2Br2, 1.07 ± 0.6; CHBr3, 12.16 ± 0.7; CBr4, 25.23 ± 0.8; CH2Br•, 41.63 ± 0.4; CHBr2 •, 48.11 ± 0.6; and CBr3 •, 55.36 ± 0.7. These data are then used to tabulate ΔH°f,T, ΔG°f,T, and K f,T for all species over the temperature range 0−1500 K. Comparison is made to existing thermochemical data through calculation of C−H and C−Br bond dissociation energies.

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Section: H°-h°0 (Kcal Molcontrasting

confidence: 70%

Structures, Vibrational Frequencies, Thermodynamic Properties, and Bond Dissociation Energies of the Bromomethanes and Bromomethyl Radicals: an Ab Initio Study

Paddison

Tschuikow‐Roux

1998

J. Phys. Chem. A

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“…However, PVF is amorphous in nature, whose structure is (CHF–CH 2 ) n . , The lifetime of polymer is determined by the cavity or trap that occurred with the electron avalanches. − The C–F bond is stronger than the C–H bond. Typically, the bond dissociation energy for C–F is about 119.5 kcal/mol compared with 103.2 kcal/mol for the C–H bond, where the C–F bond is probably 16.3 kcal/mol stronger than the C–H bond . The consequence is that the C–F bonds are more resistant to radical-induced scission than the C–H bonds.…”

Section: Resultsmentioning

confidence: 99%

Investigation on the Effect of Accumulated Charge-Induced Degradation on Multilayer Photovoltaic Insulating Backsheets Based on Atomic Force Microscopy

Zhang

Cao

Yin

et al. 2020

ACS Appl. Energy Mater.

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As a clean and renewable energy, solar energy has drawn people’s attention to mitigate the energy crisis around the world. A solar photovoltaic (PV) system is a reliable way to collect solar energy whose service lifetime is usually shorter than the designed time because of accumulated charge-induced degradation caused by electrical aging. With the rapid development of PV systems, the traditional polyethylene terephthalate (PET) backsheet cannot meet the requirements of insulation and package for the advanced solar energy system. In this context, two different backsheet materials, namely, KPK (polyvinylidene fluoride, PET, polyvinylidene fluoride) and TPT (polyvinyl fluoride, PET, polyvinyl fluoride), were selected to explore accumulated charge-induced degradation caused by partial discharge (PD) and corona discharge. In this paper, the backsheets were electrically stressed for 30, 60, and 120 min by PD and electrically stressed for 10 min by corona discharge. The accumulation and transportation of charges were investigated by phase-resolved partial discharge (PRPD) and surface potential decay (SPD). At the same time, the topography of KPK and TPT determined using atomic force microscopy after PD activity was also investigated. The explorations of PD activity showed that KPK and TPT have a similar PD resistance, but their SPD were entirely different after corona discharge. The research works in this paper provide an important path to investigate the aging process of insulating polymers and evaluate the lifetime of insulating backsheets of PV modules, as well as a guidance to improve the testing standards for the PV system.

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“…McMillen and Golden estimate the heat of formation of the CF 2 H radical at 0 K to be −59.2 ± 5 kcal mol -1 . Pickard and Rodgers have experimentally derived the heat of formation value at 298 K for CF 2 H as −57.1 ± 1 kcal mol -1 . To evaluate the heat of formation for CF 2 H, two isodesmic reaction schemes are used.…”

Section: Resultsmentioning

confidence: 99%

Coupled Cluster and Second-Order Møller−Plesset Perturbation Studies of the Mechanism of the Gas-Phase Atom−Radical Reaction of Atomic Hydrogen with CF₂ Radical

Francisco

2000

J. Phys. Chem. A

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The mechanism for the reaction of CF 2 radicals with H atoms has been examined using coupled cluster theory. There are two competing pathways for the formation of the products CF + HF. The first pathway involves direct abstraction of fluorine from CF 2 by H atoms, the barrier for which is 46.5 kcal mol -1 . The second pathway involves the addition of H atoms to CF 2 to form CF 2 H, followed by a three-center elimination of HF. The overall barrier for these two steps is 10.0 kcal mol -1 .

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Kinetics of the gas‐phase reaction CH₃F + I₂ ⇆ CH₂FI + HI: The CH bond dissociation energy in methyl and methylene fluorides

Cited by 38 publications

References 25 publications

Structures, Vibrational Frequencies, Thermodynamic Properties, and Bond Dissociation Energies of the Bromomethanes and Bromomethyl Radicals: an Ab Initio Study

Structures, Vibrational Frequencies, Thermodynamic Properties, and Bond Dissociation Energies of the Bromomethanes and Bromomethyl Radicals: an Ab Initio Study

Investigation on the Effect of Accumulated Charge-Induced Degradation on Multilayer Photovoltaic Insulating Backsheets Based on Atomic Force Microscopy

Coupled Cluster and Second-Order Møller−Plesset Perturbation Studies of the Mechanism of the Gas-Phase Atom−Radical Reaction of Atomic Hydrogen with CF₂ Radical

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Kinetics of the gas‐phase reaction CH3F + I2 ⇆ CH2FI + HI: The CH bond dissociation energy in methyl and methylene fluorides

Cited by 38 publications

References 25 publications

Structures, Vibrational Frequencies, Thermodynamic Properties, and Bond Dissociation Energies of the Bromomethanes and Bromomethyl Radicals: an Ab Initio Study

Structures, Vibrational Frequencies, Thermodynamic Properties, and Bond Dissociation Energies of the Bromomethanes and Bromomethyl Radicals: an Ab Initio Study

Investigation on the Effect of Accumulated Charge-Induced Degradation on Multilayer Photovoltaic Insulating Backsheets Based on Atomic Force Microscopy

Coupled Cluster and Second-Order Møller−Plesset Perturbation Studies of the Mechanism of the Gas-Phase Atom−Radical Reaction of Atomic Hydrogen with CF2 Radical

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Kinetics of the gas‐phase reaction CH₃F + I₂ ⇆ CH₂FI + HI: The CH bond dissociation energy in methyl and methylene fluorides

Coupled Cluster and Second-Order Møller−Plesset Perturbation Studies of the Mechanism of the Gas-Phase Atom−Radical Reaction of Atomic Hydrogen with CF₂ Radical